Teacher Guide & Answers (continued)

Meeting Individual Needs Directed Reading for Content Mastery Overview (page 19) I. Newton’s First Law A. force B. inertia II. Newton’s Second Law A. ma B. 1. gravitational a. weight b. downward 2. centripetal III. Newton’s Third Law A. opposite B. momentum; m ✕ v C. conservation of momentum Sections 1 and 2 (page 20) 1. b 6. b 2. a 7. b 3. b 8. a 4. a 9. b 5. a 10. b Section 3 (page 21) 1. Newton’s third law of motion 2. reaction 3. conservation of momentum 4. action 5. momentum 6. velocity 7. mass 8. Accept all reasonable diagrams. Key Terms (page 22) 1. gravity 2. true 3. centripetal 4. momentum 5. weight 6. true 7. Newton’s third law of motion 8. true 9. centripetal force 10. a projectile 11. first

Lectura Dirigida para la Maestría del Contenido Sinopsis (pág. 23) I. Primera ley de Newton A. fuerza B. inercia II. Segunda ley de Newton A. ma B. 1. gravitatoria a. peso b. descendente 2. centrípeta

T10 The Laws of Motion

III. Tercera ley de Newton A. opuesta B. momento; mv C. conservación del momento Secciones 1 y 2 (pág. 24) 1. b 6. b 2. a 7. b 3. b 8. a 4. a 9. b 5. a 10. b Sección 3 (pág. 25) 1. tercera ley de movimiento de Newton 2. reacción 3. conservación del momento 4. acción 5. momento 6. velocidad 7. masa 8. Acepte todas las respuestas razonables. Términos claves (pág. 26) 1. gravedad 2. verdadero 3. centrípeta 4. momento 5. peso 6. verdadero 7. tercera ley de movimiento de Newton 8. verdadero 9. fuerza centrípeta 10. un proyectil 11. perimera

Reinforcement Section 1 (page 27) 1. F = m ✕ a = 1000 kg ✕ 3 m/s2 = 3000 kg • m/s2 F = 3000 N 2. F = m ✕ a 250 N = 70 kg ✕ a 250 kg • m/s2 a= = 3.57 m/s2 70 kg 3. F = m ✕ a = 200 kg ✕ 3 m/s2 = 600 kg • m/s2 F = 600 N 4. F = m ✕ a 200 N = m ✕ 2.5 m/s2 200 kg • m/s2 m= = 80 kg 2.5 m/s2 5. A net force acting on an object causes the object to accelerate in the direction of the force. 6. the size of the force exerted and the mass of the object 7. Inertia is the tendency of an object to resist a change in its motion. 8. Let F=o in Newton’s second law. This means a=o. If a=o, then the speed is constant. Section 2 (page 28) 1. Gravity is a force that every object in the universe exerts on every other object.

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Teacher Support & Planning

Teacher Guide & Answers (continued)

2. their masses and the distance between them 3. Earth has more mass than the Moon. 4. No. The Moon exerts a smaller gravitational force than Earth. Weight is the measure of the force of gravity on an object; therefore, an object would weigh less on the Moon. 5. friction between the road and the car’s tires 6. A Dry road

B Icy road


7. Acceleration is a change in the speed or direction of a moving object. When the car changes direction to round the curve, it is accelerating. Section 3 (page 29) 1.

Figure A 2.

3. reaction force 4. action force 5. The force also will be 500 N because action-reaction forces are equal and opposite. 6. p = m ✕ v = 2 kg ✕ 10 m/s = 20 kg • m/s 7. p = m ✕ v = 2000 kg ✕ 10 m/s = 20,000 kg • m/s 8. the 2000-kg truck because it has a greater mass

Enrichment Section 1 (page 30) 1. The stitches on a baseball can change the amount of air friction on the baseball. Any factor that causes change in air friction will cause it to curve. 2. Answers will vary. Students should predict that the ball will curve better on a flat plain. Students may note that air friction is lower in the thinner air of the mountain; less friction means less curve. 3. A topspin makes the baseball move downward, or sink. A counterclockwise spin makes the ball curve to the left. A clockwise spin makes the ball curve to the right. Section 2 (page 31) Procedure 3. 35.6 s/20 swings = 1.78 s 4. 35.4 s, 35.7 s 5. 35.6 + 35.4 + 35.7/3 = 35.6 s T = 35.6 s/20 swings = 1.78 s 6. g = 4π2l/T 2 = 4(3.14)2(0.80 m)/1.78 s2 = 9.97 m/s2 Questions and Conclusions 1. 9.97 m/s2, 9.8 m/s2 2. 9.98 m/s2 – 9.97 m/s2/9.8 m/s2 ✕ 100 = 1.7% 3. Answers will vary. 4. By timing many swings, the error in starting and stopping the clock is a smaller fraction of the total time being measured. Section 3 (page 32) Table 2 Kiran, 85.0 kg; Monique, 75.0 kg; Tracey, 93.0 kg; Chandra, 84.2 kg; Alexis, 103.1 kg; Sophia 95.0 kg Table 3 line: Tracey, Alexis, great strength back: Kiran, Monique, small and fast end: Chandra, Sophia, strong and fast

Note-taking Worksheet (page 33) Figure B

Refer to Teacher Outline; student answers are underlined.

Assessment Chapter Review (page 37) Part A. Vocabulary Review 1. Newton’s third law of motion (8/3) 2. inertia (3/10) 3. projectile (6/2) The Laws of Motion T11



4. centripetal acceleration (7/2) 5. centripetal force (7/2) 6. Newton’s first law (1/1) 7. Newton’s second law of motion (1/1) 8. momentum (9/3) 9. conservation of momentum 10. Gravity (4/2) 11. weight (5/2) 12. distance (4/2) 13. newtons (5/2) Part B. Concept Review 1. (4, 7/2) Satellite a

c

Chapter Test (page 39)

b

Orbit path 2. (6/2)

Inertia

Result g

3. They will strike the floor at the same time because gravity pulls both balls toward the floor with the same force. (4/2) 4. P = m ✕ v P = 2 kg ✕ 20 m/s P = 40 kg • m/s (9/3) 5. Air resistance on the flat sheet of paper is greater because of its shape, therefore it would fall more slowly than the wad of paper. (3/1) 6. when it is in free fall or when it appears to be free from the effects of gravity (5/2) 7. The momentum before is equal to the momentum after. P = mv = 2 kg ✕ 10 m/s = 20 kg • m/s = (2 kg + 2 kg) ✕ v The final speed is 5 m/s.

T12 The Laws of Motion

I. Testing Concepts 1. c (2/5) 13. a (7/2) 2. c (2/1) 14. c (8/3) 3. d (8/3) 15. d (8/3) 4. a (7/3) 16. b (4/2) 5. b (7/3) 17. a (9/3) 6. a (5/2) 18. d (7/2) 7. b (1/1) 19. b (1/1) 8. d (10/3) 20. c (2/6) 9. b (2/6) 21. c (4/1) 10. c (3/1) 22. c (7/2) 11. d (4/2) 12. d (6/2) II. Understanding Concepts 1. Answers will vary, but should reflect the idea that changing shapes of one or both pieces of paper will cause the amount of air resistance affecting the sheets of paper to differ. (3/1) 2. A. 250 kg • m/s (9/3) B. 12 kg (9/3) C. 12 m/s (9/3) D. 20 kg (9/3) 3. a. D (9/3) b. A (9/3) c. They have the same momentum. (9/3) d. Object B has a greater mass than object A. (9/3) e. Object D has a greater velocity than object C. (9/3) 4. The ball loses momentum. (10/3) 5. The pins gain momentum equal to that lost by the ball. (10/3) III. Applying Concepts 1. F = m ✕ a = 12 kg ✕ 4 m/s2 = 48 kg • m/s2 F = 48 N (1/1) 2. F = m ✕ a 300 N = 25 kg ✕ a 300 kg • m/s2/25 kg = a a = 12 m/s2 (1/1) 3. F = m ✕ a 3000 N = m ✕ 15 m/s2 3000 kg • m/s2/15 m/s2 = m m = 200 kg (1/1) IV. Writing Skills 1. The amount of air resistance is greater on the larger, flatter object. Since gravity accelerates all samples of matter at the same rate, the air resistance is what slows the larger object’s fall. The greater the amount of air resistance on the larger object pushes up on the object as gravity pulls it down. (3/1) 2. Answers will vary, but may include such activities as jumping rope, running, or throwing a ball. (4/1) 3. Mass is a measure of the amount of matter in an object; it is measured in grams and kilograms. Weight is a measure of the force of gravity on an object. It is measured in units called newtons. (5/2)




Teacher Guide & Answers (continued)

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